Installed the PPA the right way, still no dice. I wonder if we are chasing ghosts with this libzen issue. Everything seems to get indexed fine (which is, as I understand it, what mediainfo is used for), it's the playback that fails.

if you have a working version, can you try to playback an mp4 file? Here is the command that actually streams the file

You can try experimenting with different library paths (see the instructions under "For Debian, the relevant information is stored here" in issue 1152 and adjust accordingly) and/or temporarily adding symlinks as per the original ticket. I'm still using 10.10, so it's not something I can reproduce.